For some late ideas, your crew skills depend on how you use it.
If you redline snipe from behind everyone then use GLD, vents and optics. Also use camo. Or just forget trying to turn a brawling masterpiece into a bad TD. The low alpha means you will have to expose yourself constantly to get damage. Sniping TDs do a lot better with a big alpha strike every so often, not a barrage of tiny pin-pricks.
Sniping in a Crommie is like keeping an Orca in your backyard swimming pool. Let it out into its natural habitat.
If you use it like the vast majority of people then its all about brawling - close range DPM. Set it up like Ezz and most of the others have recommended. Early pressure and map control win games and the Crommie(B) excels at that. I averaged 2.3 spots per game in my CrommieB with a 62% WR. The Crommie was played very early in my scrub days and still managed a 55% WR in it.
Because you are brawling, prioritising repairs over camo is the wise choice. You are definitely going to be spotted when you are brawling, so camo gives you bugger all benefit. Gun handling skills on driver and gunner will help, but you are generally so close it won't matter - they will help you slightly longer range fights.
And get controlled impact. A Crommie will kill a full health T37 with one shot and a followup ram. Get controlled impact.